The present application relates generally to the field of aircraft display systems.
The present invention more particularly relates to aircraft systems configured to generate a radar derived perspective terrain display and methods for the same.
Aircrafts often include a number of aircraft display systems that show, indicate, or otherwise display situational information to the occupants of the aircraft, typically the pilots. For example, aircraft display systems typically display weather, aircraft diagnostics and communications information. Some aircraft display systems also display terrain. Terrain displays show some type of visual indication of terrain determined to be ahead of or below the aircraft.
Terrain awareness and avoidance mechanisms are important features of modern aircraft. A variety of terrain awareness systems have been developed to provide the pilot heightened levels of terrain awareness. These solutions include ground proximity warning systems, database terrain awareness and warning systems, synthetic vision database displays, and enhanced vision sensors. Each of these techniques suffer from a number of challenges or problems. For example, the database driven solutions use sensed position, aircraft altitude, and terrain database information to build a terrain display. These database driven solutions are limited by the accuracy and completeness of the database and the accuracy of a sensed navigation position. Due to the speeds at which aircraft travel, inaccuracies and errors in the database and position sensor are undesirable.
Database driven solutions and enhanced vision sensor solutions typically utilize only a plan or overhead display view of terrain. This solution is undesirable because it is difficult for pilots to quickly determine absolute and relative altitude of the various terrain features shown in the display. Some systems also include vertical situation displays that show a side or horizontal view of terrain altitude. This solution is also undesirable because it is difficult for pilots to quickly determine the proximity or range of the various terrain features shown on the display in relation to the aircraft. Furthermore, if weather and navigational elements are shown on the same display as the terrain features, it may be difficult for a pilot to distinguish displayed weather elements and navigational elements from terrain details because of the display image's two dimensional nature.
Horizontal views provide for the graphical display of terrain altitude ahead of the aircraft, but are typically only capable of displaying the terrain along the heading line of the aircraft. This narrow view of the terrain ahead of the aircraft means that the pilot may not be made aware of maneuver options that are available to avoid obstacles. For example, if an aircraft were headed directly for a water tower, the display would show an obstacle at a fixed height and an undetermined width directly in front of the aircraft. The pilot would not be able to distinguish a water tower from a mountain or an infinite wall because the obstacle's width, even if relatively narrow, would extend across the entire display. With such a narrow view, the pilot would determine that the only option for avoiding the object is to increase altitude. While increasing altitude would be ideal for an infinite wall of a fixed height, other maneuvers or combinations of maneuvers might be more effective for avoiding objects of very narrow width or whose height tapers up or down, such as a water tower or a mountain. To avoid the water tower, the pilot might decide to turn the aircraft to the left or right rather than increase altitude, or to avoid a mountain that tapers up to the left and down to the right, the pilot might simultaneously turn the craft to the right and increase altitude.
Plan view and horizontal view terrain displays typically suffer from an additional display problem if aircraft-based radar is used to detect terrain. Aircraft-based radar cannot determine the altitude of terrain areas behind tall terrain features because of the radar-blocking nature of terrain. Indeterminable terrain blocked from the view of radar is referred to as “radar shadow” and may result in missing portions or incorrect portions on a horizontal or plan terrain displays. Radar shadow is undesirable because it presents an unnatural or broken terrain view which results in a display that is difficult for a pilot to read. Furthermore, radar shadow adds another element to the display that the pilot needs to recognize and interpret properly.
Terrain or ground warning systems which do not provide a complete display of terrain may provide a less than an optimal amount of information to pilots. Some systems, for example, will trigger a warning when an aircraft's flight path is determined to be on a collision path or close to a collision path with terrain elements. In the absence of an easy to read and highly indicative terrain detail display, the pilot may only attempt pulling-up when a complete terrain display might have indicated that an easier route would have been to pull up and turn to the left, for example.
Consequently, there exists a need for improved methods and systems for accurately displaying radar derived terrain information in a broad perspective view that allows the pilot to gauge the height, range and contour of the terrain features near the aircraft to make appropriate terrain avoidance maneuver decisions.
It would be desirable to provide a system and/or method that provides one or more of these other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the aforementioned needs.